Clean up a couple more URI alter() calls

Summary:
See <https://discourse.phabricator-community.org/t/create-new-phriction-document-fails-with-unhandled-exception-invalidargumentexception/2406>.

These weren't obviously nullable from a cursory `grep`, but are sometimes nullable in practice.

Test Plan: Created, then saved a new Phriction document.

Reviewers: amckinley

Reviewed By: amckinley

Differential Revision: https://secure.phabricator.com/D20184

src/applications/phriction/editor/PhrictionTransactionEditor.php

@@ -229,9 +229,14 @@ final class PhrictionTransactionEditor
     foreach ($xactions as $xaction) {
       switch ($xaction->getTransactionType()) {
         case PhrictionDocumentContentTransaction::TRANSACTIONTYPE:
-          $uri = id(new PhutilURI('/phriction/diff/'.$object->getID().'/'))
+          $params = array(
-            ->alter('l', $this->getOldContent()->getVersion())
+            'l' => $this->getOldContent()->getVersion(),
-            ->alter('r', $this->getNewContent()->getVersion());
+            'r' => $this->getNewContent()->getVersion(),
+          );
+
+          $path = '/phriction/diff/'.$object->getID().'/';
+          $uri = new PhutilURI($path, $params);
+
           $this->contentDiffURI = (string)$uri;
           break 2;
         default:

src/view/phui/PHUITimelineView.php

@@ -154,8 +154,21 @@ final class PHUITimelineView extends AphrontView {
       }
 
       $uri = $this->getPager()->getNextPageURI();
-      $uri->replaceQueryParam('quoteTargetID', $this->getQuoteTargetID());
+
-      $uri->replaceQueryParam('quoteRef', $this->getQuoteRef());
+      $target_id = $this->getQuoteTargetID();
+      if ($target_id === null) {
+        $uri->removeQueryParam('quoteTargetID');
+      } else {
+        $uri->replaceQueryParam('quoteTargetID', $target_id);
+      }
+
+      $quote_ref = $this->getQuoteRef();
+      if ($quote_ref === null) {
+        $uri->removeQueryParam('quoteRef');
+      } else {
+        $uri->replaceQueryParam('quoteRef', $quote_ref);
+      }
+
       $events[] = javelin_tag(
         'div',
         array(